add rust lint ignore for match cmp

[dpaiton]

Rust lint (clippy) suggests we make a change from

if x < y
else if x > y
else

to

match x.cmp(y)
ordering.less
ordering.greater
ordering.equal

This is a pretty controversial lint suggestion from clippy. @jalextowle and I talked about it and we both agree that the original formatting is better (more readable, doesn't require extra import). We should set a global ignore for this lint warning.